1. Field of the Invention
The present invention relates to a reducer of an electric power auxiliary steering apparatus. More particularly, the present invention relates to a reducer of an electric power auxiliary steering apparatus in which impulse noise of a worm shaft bearing caused by fluctuation of a worm shaft can be reduced, and strength of a damping member in a direction toward a worm wheel and an opposite direction thereto is lower than that in other directions, so that the fluctuation of the worm shaft can be more effectively alleviated.
2. Description of the Prior Art
FIG. 1 is a sectional view illustrating a reducer of an electric power auxiliary steering apparatus according to the related art.
As illustrated in FIG. 1, the reducer 100 of the electric power auxiliary steering apparatus according to the related art is provided with a worm shaft 103 formed with a worm 101 on an outer peripheral surface thereof. Worm shaft bearings 105A and 105B are mounted at opposite ends of the worm shaft 103 to support the worm shaft 103. In order to prevent the worm shaft bearing 105B from moving in an axial direction of the worm shaft 103, a plug bolt 107 is fastened between a damping coupler 109 and the worm shaft bearing 105B and fixed by a plug nut 111.
The worm shaft 103 is connected with a motor shaft 115 of a motor 113 through the damping coupler 109, and is rotated by driving of the motor 113.
A worm wheel 117 is provided at a side of the worm 101 and engaged with the worm 101 formed on the worm shaft 103. The worm wheel 117 is mounted to a steering shaft 119 for transferring a rotating force of a steering wheel (not illustrated) operated by a driver, and a rotating force of the worm shaft 103 by the driving of the motor 113 is transferred to the steering shaft 119.
The worm shaft 103, the worm wheel 117, and the like are embedded in a gear housing 121, and the motor 113 providing a driving force to the worm shaft 103 is provided at a side of the gear housing 121. A motor cover 123 coupled to the motor 113 and the gear housing 121 are coupled to each other through a bolt 125.
Balls 131 are interposed between an inner race 127 and an outer race 129 of the worm bearing 105B so that the worm bearing 105B supports the rotating worm shaft 103 connected with the motor shaft 115 of the motor 113.
In the reducer of the electric power auxiliary steering apparatus having such a structure as described above, an electronic control device provided to a vehicle controls the motor 113 according to driving conditions of the vehicle, and the rotating force of the worm shaft 103 by the driving of the motor 113 is added to the rotating force of the steering wheel operated by the driver and transferred to the steering shaft 119, so that the steering driving state of the driver can be maintained softly and stably.
However, with the use of the reducer of the electric power auxiliary steering apparatus according to the related art, a clearance between the worm shaft rotated by the driving of the motor and the worm wheel engaged with the worm formed on the worm shaft is increased by friction, thus resulting in noise and inaccurate provision of the auxiliary steering force subsidiary to the steering wheel operating force of the driver.